This is a bitfield oriented enum, with the following bits:
bit 0 - spent
bit 1 - appears in alt chain
bit 2 - appears in best chain
bit 3 - double-spent
bit 4 - pending (we would like the tx to go into the best chain)
Not all combinations are interesting, just the ones actually used in the enum.

valueOf

Returns the enum constant of this type with the specified name.
The string must match exactly an identifier used to declare an
enum constant in this type. (Extraneous whitespace characters are
not permitted.)